The primary objective of this study is to collect safety information on rabeprazole 10 mg and 20 mg in the treatment of gastroesophageal reflux disease (GERD) in children aged 12 to 16 years. The secondary objectives are to assess the efficacy of rabeprazole on the improvement of the symptoms of GERD and to explore the relationship of symptom relief to dose received, based on symptom frequency and severity, antacid use, and quality of life (QOL) measures.

Inclusion Criteria:

1. Males and females aged 12 to 16 years with a clinical diagnosis of symptomatic GERD or suspected or endoscopically proven GERD.
2. Patients who have ever been treated with, or are currently receiving proton pump inhibitors (PPIs),histamine receptor (H2) blockers, or antacids are eligible (as long as they can go off PPIs and H2 blockers for three days prior to dosing, except for cimetidine, which must be discontinued for at least seven days prior to dosing; exclusion criteria 5 and 6). Also, patients should be able to go off PPI therapy for two weeks at the end active drug treatment.
3. Children with stable asthma/reactive airways disease on stable treatment regimens are eligible.
4. Children on stable doses of allergy, antiepileptic, antidepressant, and attention deficit disorder medicines are eligible.
5. Patients must be able and willing to swallow the test drug tablet intact. The ability of the child to swallow an intact tablet must be confirmed by the site at Screening.
6. The patient is willing and able to give assent to participate.
7. The patient's parent or guardian gives written informed consent.
8. Post-pubertal females will be required to be abstinent during the course of the study.
9. Clinically insignificant laboratory findings.

Exclusion Criteria:

1. Evidence of significant hepatic, renal, respiratory, endocrine, immune, infectious, hematologic, neurologic, psychiatric, or cardiovascular system abnormalities that would interfere with the conduct of the study, the interpretation of study results, or the health of the patient during the study.
2. History of primary esophageal motility disorders or systemic condition affecting the esophagus (eg, scleroderma, esophageal infections).
3. History of eosinophilic esophagitis, persistent milk protein allergy, or allergic gastroenteropathy. History or current presence of peptic ulcers; current presence of Helicobacter pylori.
4. History of definitive acid-lowering surgery, previous esophageal surgery, or esophageal stricture is disallowed. History of fundoplication or feeding tube insertion is allowed.
5. Treatment with full therapeutic doses of H2-receptor antagonists or sucralfate within three days prior to dosing (or a shorter washout if agreed to by Investigator and Sponsor), except for cimetidine, which must be discontinued for at least seven days prior to dosing.
6. Treatment with a proton pump inhibitor within three days prior to dosing (or a shorter washout if agreed to by Investigator and Sponsor).
7. Inability to have 2-week PPI therapy-free period at end of active drug treatment.
8. Pregnancy or lactation.
9. Known or suspected drug addiction or alcohol abuse and/or a positive urine drug screen not explained by medication list; occasional alcohol or tobacco use is not an exclusion criterion.
10. Unwilling or unable to abide by the requirements of the study or violating the prohibitions and restrictions of the study defined in Section 9.4.
11. Any condition which would make the patient, in the opinion of the Investigator or Sponsor, unsuitable for the study.
12. Participation in another investigational drug study within one month prior to dosing.
13. A history of allergy/sensitivity to proton pump inhibitors or to their inactive ingredients.